I was reading a story and the author mentioned that the super-special element made up only half of a percent of the crust. That actually seemed rather large to me, so I googled "composition of the earth's crust" and found the paper The Composition of the Earth's Crust. Isn't nice when things work out like that.

The section on the crust does not get more specific than 1% (page 39 of pdf), so I went to the next best thing, the section on igneous rocks (page 25 of pdf). That is when things got weird. Apparently, uranium makes up 0.8% and zinc makes up 0.4%. It gets even worse with lead being 0.2%. I went to the next page for an explanation, and found another table that gives different values for these same elements in MUCH smaller amounts. So I repeat: .

P.S. What notation is being used on columns 2 and 4 of the table on page 25. At first I thought that it was regular decimal notation, but that would mean that thier estimations for 5 elements, including copper, changed by >2 degrees of magnitude.

According to Jefferson Lab, Uranium has an abundance of 2.7 ppm in the crust and 3.2 ppm in the ocean. Zinc has an abundance of 70 ppm in the crust and 49 ppm in the ocean, while lead has 14 ppm and 0.03 ppm, respectively. That's a pretty big difference.

I had a cursory glance at the tables, and couldn't quite determine whether the quantities were molar (number of atoms), by weight (each uranium atom is roughly 11/3rds the weight of a zinc one) or by density (pure uranium seems to be roughly 8/3rds that of pure zinc, but compounded/alloyed, with the other thibgs like silicon, that'd change).

There's a bit that discusses the percentage masses of lithosphere, hydrosphere and atmosphere near one of the tables, but my brief skim (around the two tables referenced in the OP) when the question first came up didn't reveal the measure. Could there be an internal inconsistency?

Edit: TIL that noble metals are actually rare due to their nobility. Since they do not react to form stone-like materials, they do not float on iron. And therefore most Gold$$$$ has sunk to the core of the earth. Makes perfect sense, but I never connected the dots there. Would this work for bitcoins?

If the heavier elements sink to the core, would that mean uranium sinks to the core too? Its density is almost the same as gold. Is most of the uranium in the core perhaps? What's the ppm of uranium in the entire earth and/or core?

Yes, solubility is a key thing. Uranium will form compounds and go into rock more readily than gold. Since it doesn't fit well in many crystal lattices it is also one of the last components to crystallize in a cooling magma. As a result it tends to get concentrated in continental crust.